The following description is provided to assist the understanding of the reader. None of the information provided or references cited is admitted to be prior art to the present invention.
Diseases and degenerative conditions of the optic nerve and retina are the leading causes of blindness in the world. A significant degenerative condition of the retina is age-related macular degeneration (ARMD). ARMD is the most common cause of blindness in people over 50 in the USA and its prevalence increases with age. ARMD is classified as either wet (neovascular) or dry (non-neovascular); the dry form of the disease is more common. Macular degeneration occurs when the central retina has become distorted and thinned usually associated with age but also characterized by intra-ocular inflammation and angiogenesis (wet ARMD only) and/or intra-ocular infection. The subsequent generation of free radicals, resulting in oxidative tissue damage, local inflammation and production of growth factors (such as VEGF and FGF) and inflammatory mediators, leads to inappropriate neovascularisation in common with the wet form of ARMD.
Retinopathy is a leading cause of blindness in type I diabetes, and is also common in type II diabetes. The degree of retinopathy depends on the duration of diabetes, and generally begins to occur ten or more years after onset of diabetes. Diabetic retinopathy may be classified as non-proliferative, where the retinopathy is characterized by increased capillary permeability, edema and exudates, or proliferative, where the retinopathy is characterized by neovascularisation extending from the retina to the vitreous, scarring, deposit of fibrous tissue and the potential for retinal detachment. Diabetic retinopathy is believed to be caused by the development of glycosylated proteins due to high blood glucose. Several other less common retinopathies include choroidal neovascular membrane (CNVM), cystoid macular edema (CME), epi-retinal membrane (ERM) and macular hole.
Glaucoma is made up of a collection of eye diseases that cause vision loss by damage to the optic nerve. Elevated intraocular pressure (IOP) due to inadequate ocular drainage is the primary cause of glaucoma. Glaucoma often develops as the eye ages, or it can occur as the result of an eye injury, inflammation, tumor or in advanced cases of cataract or diabetes. It can also be caused by the increase in IOP caused by treatment with steroids. Drug therapies that are proven to be effective in glaucoma reduce IOP either by decreasing vitreous humor production or by facilitating ocular draining. Such agents are often vasodilators and as such act on the sympathetic nervous system and include adrenergic antagonists.